The mammalian target of rapamycin (mTOR) is a central regulator of cell growth and proliferation and plays a gatekeeper role in the control of cell cycle progression. The mTOR signaling pathway, which integrates both extracellular and intracellular signals, is activated in certain cellular processes such as tumor formation, angiogenesis, insulin resistance, adipogenesis, and T-lymphocyte activation. In addition, the mTOR signaling pathway is deregulated in diseases such as cancer and type 2 diabetes. See Laplante et al., J. Cell Science 122, pp 3589-3593 (2009).
mTOR mediates mitogenic signals from PI3K/AKT through to the downstream targets S6K1 (ribosomal S6 kinase 1), 4E-BP1 (eukaryotic translation initiation factor 4E-binding protein) and AKT. Recently, it has been shown that mTOR exists in two complexes. Raptor-mTOR complex (mTORC1) is a rapamycin-sensitive complex that phosphorylates S6K1 and 4E-BP1. Rictor-mTOR complex (mTORC2) is a rapamycin-insensitive complex that phosphorylates AKT at Ser473. Although the precise mechanism by which rapamycin inhibits mTOR function is not well understood, rapamycin partially inhibits mTOR function through mTORC1. Since mTORC2 is involved in the regulation of cell survival, metabolism, proliferation, and cytoskeletal organization in a rapamycin-independent manner, complete inhibition of mTOR function through inhibition of both mTORC1 and mTORC2 may lead to a broader spectrum antitumor activity in the treatment of cancer or better efficacy. In addition, inhibition of both mTORC1 and mTORC2 may lead to better efficacy in treating other diseases than through inhibition of mTORC1 alone.
There exists a need in the art for small-molecule compounds having desirable physicochemical properties that are useful for treating cancer and other disorders associated with deregulated mTOR activity. Specifically, there exists a need for small molecule inhibitors of mTOR kinase that block signaling through mTORC1 and mTORC2 for treating cancer and other disorders.